Traditionally the transport of media streams between a server and client has been assumed to be over links with a single homogeneous transport layer e.g. all RTP over IP (Real-time Transport Protocol over IP), all TDM (Time-Division Multiplexing) or all MPEG-TS (MPEG transport stream).
Cable companies now wish to change from MPEG-TS servers and clients to IP servers and clients. The motivation for the transfer from MPEG-TS servers and clients to IP servers arises due to the desire for Video Entertainment delivery to move from a conventional broadcast structure to a personalized unicast structure. At present in a typical Cable TV network, the distribution of digital entertainment is done over a Hybrid fibre-coaxial (HFC) network as MPEG-TS packets in 6 MHz QAM (Quadrature amplitude modulation) channels. The movement from broadcast to “personalized” unicast is coming, but there is insufficient bandwidth in the IP DOCSIS transport to support the number of viewers that is currently supported by broadcast.
The move from broadcast to unicast therefore requires a massive increase in the capacity of the installed Metro Network. While it is relatively easy and inexpensive to convert the core of the network to operate using an IP based protocol, the HFC first mile or access network would have to be completely changed out for another technology if all the video carried over it today was to be delivered as (unicast) IP packet media streams.
Conventionally approaches to this problem involve keeping two networks in place until there has been a complete changeover to IP everywhere. This approach incurs considerable cost in the First Mile, for example by increasing the IP capacity of Data Over Cable Service Interface Specification (DOCSIS) with node splitting and channel bonding a 1a DOCSIS 3.0, or by overbuilding with a FTTH (Fibre to the Home) solution. Such approaches result in extra costs due to server duplication and change out of clients. A convenient mechanism for managing the transition from the existing delivery system to one based around IP servers and IP clients is therefore required.